The present invention relates generally to a mobile accommodation structure and particularly to such a structure provided with an extension unit by which it is possible to extend the available volume within the structure, and to an extension unit for use on a mobile accommodation structure.
The term "mobile accommodation structure" will be understood herein to refer to any rigid or semi-rigid structure usable as accommodation for personnel, whether for domestic, industrial or business purposes. The present invention will be described hereinafter with particular reference to its application to towable caravans, but this description is presented without prejudice to the generality of the invention which can be applied to mobile accommodation structures whether provided with wheels or not, and which are adapted to be moved in one way or another from one place to another In particular, it is intended that the present invention be applicable not only to caravans, but also to portable buildings adapted to be lifted onto and transported by transporter lorries, and also to such lorries and vans themselves, which are often provided with a body intended to be used for accommodation of goods and personnel, particularly when stationary. This is especially the case with vans used by roundsmen or mobile salesmen, where it is advantageous to be able to enlarge the space within the vehicle whilst stationary and available for sales, but to reduce the size of the vehicle for transport from place to place. The same principle of operation can be applied to railway vehicles to enlarge the accommodation space when stationary and reduce it when travelling.
The convenience of a reduction in size of a towable vehicle such as a caravan is well known and a number of attempts to provide caravans and like such mobile accommodation structures with expansion units have been made. Perhaps the most widely successful is the structure described in published European Patent application No. 006072 which includes wall and roof panels which can be folded down into a very small volume for towing purposes, and enlarged, when stationary by erection of the folded wall panels from a position within the trailer to an erected position where they define a relatively large volume. Other structures having this general configuration are known, and the major disadvantage of these, apart from the relatively long time taken to convert from the collapsed to the erected position (and European Patent application 006072 is particularly concerned with an improvement of such a structure whereby it can be erected and collapsed entirely automatically using hydraulic or pneumatic means) lies in the fact that, when collapsed to form a trailer, the walls and roof of the structure occupy the majority of the internal space of the trailer so that relatively little space is left for furnishings and/or clothing which may be wanted.
Various other proposals have been made for enlarging the usable volume of a caravan, particularly by the use of tent-like awnings and/or folding panels which lie alongside the side wall of the caravan when collapsed. Once such structure is described in British Patent application No 2,174,732A which discloses a structure such as a portable building or the body of a vehicle or trailer defining an internal space which is rectangular in plan. Each of a pair of opposite side walls of the structure has an aperture closable by hinged flaps which are openable to form the base, top and walls of an extension enlarging the normal internal space of the structure. The outward extensions, when erected, form an enlarged central region extending laterally from the normal internal space of the structure, and this may be partitioned by inclined partitions to form the main compartment of the portable building when erected.
A primary disadvantage of the structure disclosed in the above Patent lies in the fact that the two side wall panels, when folded to the collapsed position, overlie one another so that it is in practice not possible to fit either side wall with a door or window usable in both the erected and collapsed positions. The user then does not have any choice as to whether to erect the extension or to use the structure in the collapsed state but is forced always to extend the structure into its erected condition in order to make it usable.